The Gouldian finch (Erythrura gouldiae), also known as the Lady Gouldian finch, Gould's finch or the rainbow finch, is a colourful passerine bird endemic to Australia. There is strong evidence of a continuing decline, even at the best-known site near Katherine in the Northern Territory. Large numbers are bred in captivity, particularly in Australia. In the state of South Australia, National Parks & Wildlife Department permit returns in the late 1990s showed that over 13,000 Gouldian finches were being kept by aviculturists. If extrapolated to an Australia-wide figure this would result in a total of over 100,000 birds. In 1992, it was classified as "endangered in the wild" under IUCN's criteria C2ai. This was because the viable population size was estimated to be less than 2,500 mature individuals, no permanent subpopulation was known to contain more than 250 mature individuals, and that a continuing decline was observed in the number of mature individuals. It is currently subject to a conservation program.

The Gouldian finch was described by British ornithological artist John Gould in 1844 and named after his wife Elizabeth. It is also known in America as the rainbow finch, Gould's finch, or the Lady Gouldian finch (although Mrs. Gould did not hold the title lady). In Australia, it is predominantly called the Gouldian finch. It is a member of the weaver-finch family Estrildidae, which is sometimes considered a subfamily of Passeridae.

Both sexes are brightly coloured with black, green, yellow, and red markings. The females tend to be less brightly coloured. One major difference between the sexes is that the male's chest is purple, while the female's is a lighter mauve.

Black headed female Gouldian finch

Gouldian finches are about 130–140 mm long. Gouldian finches' heads may be red, black, or yellow. Formerly considered three different kinds of finches, it is now known that these are colour variants that exist in the wild.[3]Selective breeding has also developed mutations (blue, yellow and silver instead of a green back) in both body and breast colour.

Juveniles also have distinctive colours. Their heads, sides and necks are grey, and their backs, wings and tail feathers are olive green. Their undersides are pale brown. Beaks are blackish with a reddish tip. Their legs and feet are light brown. Newly hatched Gouldian finches are pink and naked until about 12 days old when the beginnings of feathers start to appear. Very young birds, like many other species of Australian cavity-nesting finches, have a variety of odd features in and around their mouths including a "palate marked in the fashion of a domino" and several "prominent rounded tubercles" with an "opalescent lustre" at the back of the gape. These tubercles are commonly (and incorrectly) described as phosphorescent in spite of much scientific evidence to the contrary.[4] It is believed that these tubercles simply reflect light and are not luminescent.[4] Scientists have hypothesized that this domino-like palate and striking tubercles may facilitate feeding within the dark confines of a nest cavity, although no experiments have been conducted to support this idea.

Prior to the Australian government's ban on the export of Australian fauna in 1959, Gouldian finches were exported worldwide. These birds have resulted in viable breeding populations being held in many countries.

Captive breeding has resulted in several colour mutations to the back and two mutations to the breast. Mutations vary by country, with some existing only in Australia (the Australian yellow and the Australian "dilute") and others existing in greater number in the United States, such as the blue bodied Gouldian. The most common body mutations in the United States are blue, pastel green (single and double-factor, resulting in "dilute" and yellow males and yellow females), and pastel blue (again, single and double-factor producing "pastel" and silver males, and silver hens).[6] There is also a lutino and albino mutation in the United States, established by Winnie McAlpin of Delmar Aviaries.[7]

The number of Gouldian finches has decreased quite dramatically during the 20th century. Their habitat has been reduced or altered. Early research indicated a parasite called the air sac mite was responsible for the decline of the species. This is no longer considered to be a major factor. In general, Gouldian finches are susceptible to diseases and viral infections. Their beautiful colours mean that they are easily caught by predators. Fires are listed as the primary threat to the natural populations. The total number of Gouldian finches altogether is not low, however, because they are among the most popular pet birds, and are bred in captivity for the pet trade.

Recovery plans are in place to recover and conserve its natural habitats, such as building protective fencing to prevent damage by cattle, research on wildfires and their effects on Gouldian population[8] and constructing artificial nest boxes in order to provide more nesting locations for wild pairs.[9] Attempts at reintroduction have so far proved unsuccessful. It was also suggested to develop management guidelines for land-holders about appropriate land management, promoting the recovery program, and Gouldian finch conservation.

Although often bred in a colony in captivity, in the wild, the Gouldian is not a colony bird. Outside the breeding season, however, Gouldian finches often join mixed flocks consisting of long-tailed finches and masked finches. This is probably a defense against predation. Flocks used to consist of up to 1,000–2,000 individuals. During the breeding season they are usually found on rough scree slopes where vegetation is sparse. In the dry season, they are more nomadic and will move to wherever there is food and water.

Like other finches, the Gouldian finch is a seed eater. During the breeding season, Gouldian finches feed mostly on ripe or half-ripe grass seeds of sorghum. During the dry season, they forage on the ground for fallen seed. During the wet season, spinifex grass seed (Triodia sp.) is an important component of their diet. So far Gouldians have been recorded as consuming six different species of grass seed, but during crop analysis, researchers have yet to find evidence of insect consumption.

Gouldian finches generally make their nests in tree-holes, generally within a kilometer or so of water. They usually breed in the early part of the dry season, when there is plenty of food around. The male courtship dance is a fascinating spectacle. When a male is courting a female, he bobs about ruffling his feathers to show off his colors. He expands his chest and fluffs out his forehead feathers. After mating, a female lays a clutch of about 4–8 eggs. Both parents help brood the eggs during the daytime, and the female stays on the eggs at night. When the eggs hatch, both parents help care for the young. Gouldian finches leave the nest at between 19 and 23 days and are independent at 40 days old.

Gouldian finches have brightly coloured gapes and call loudly when the parent birds return so that they are able to find and feed their mouths in the dark nest.[11]

Young Gouldians are very fragile until their final moult. Some breeders believe parent-raised Gouldians have greater success rearing young than those fostered by other species, such as Society finches or spice finches.

It has been shown scientifically that female finches from Northern Australia are controlling the sex of their offspring, according to the head color of their male counterpart.The finding, published in the journal Science, is one of the first to clearly show that birds are capable of biasing the sex of their offspring to overcome genetic weaknesses.[12] This has also been reported in the ABC television scientific program Catalyst.[13] Lead author Dr Sarah Pryke, of the Department of Brain Behaviour and Evolution at Macquarie University in Sydney, admits the mechanism by which the birds do this is not yet known.

The Gouldian finch (Erythrura gouldiae), which is found in the northern savannahs of Australia, can have black, red or orange heads. Pryke says some genetic incompatibility between the black and red-headed birds results in high mortality in the offspring when birds of different head colours mate. With female offspring this mortality rate can be as much as 80% higher than in a same-head colour pairing. Sons in a mixed pairing have a 40% mortality rate. Pryke found that if the female mates with a finch of different head colour, she attempts to overcome this genetic incompatibility by over-producing sons – as much as four males to one female. "This jis the first time such a large effect has been shown," says Pryke. "It is actually the female that is controlling the gender." To reach this conclusion Pryke and colleague Simon Griffith took 100 red-headed and 100 black-headed female birds and mated them with a male of the same head colour and a male with the different head colour. They found females in mixed pairs produced broods that were 82.1% male, whereas females in matched pairs produced an unbiased sex ratio with 45.9% males. They then tested whether the females in mixed pairs were deliberately over-producing sons. In captivity the female finches often need worming, this is a common thing with all female finches. Female birds were tricked into thinking they were mating with an incompatible male. The researchers did this by temporarily blackening the head colour of red males and mating them with red and black-headed females. The black females paired to red males with blackened heads produced a sex ratio that was roughly equal. By contrast, red females paired with red males that had blackened heads over-produced sons at a ratio similar to a mixed pairing. Pryke says there is no chemical or genetic interaction between the parents at work. "Gouldian finches wear their genes on their head so it is easy for a female to assess the genetic suitability of the male," she says. "Change the colour of the male's head with dye and the sex ratio changes." Through the study the researchers also found that females from mixed pairs produced fewer and smaller eggs. Pryke says the finding is important because up to 30% of breeding pairs in the wild are mixed "perhaps because of constraints on preferred mate availability".

Professor Ben Sheldon, director of the University of Oxford's Edward Grey Institute of Field Ornithology, says the results demonstrate "hitherto unsuspected degrees of control over reproductive investment by female birds". "This work opens new possibilities in unravelling the mechanisms behind these striking behaviours, something which has up to now remained an unsolved mystery," he says.[14][15][16]

Gouldian finches are a popular species in aviculture due to their bright colors, low maintenance, and relative easy breeding. A high-quality finch seed blend, fresh clean water daily, and grit mixture (soluble and insuloble) are components of an every day diet that should be considered along with fresh dark leafy greens (Kale, Collards, Chard) and egg-food or soft-food offered two to three times a week when not breeding, and daily while breeding.

They are a colony bird so it is not recommended to keep them alone, and they get along well with other species of grass finch as well as other docile species such as waxbills and parrot finches, though one should exercise caution when housing the latter two together as they will hybridize.

In the Kimberley District of Western Australia, where most wild Gouldian Finch were trapped for aviculture, it was often reported as one of the more common of the eleven finch species. Until 1977, it was trapped in greater numbers than any other finch. From 1897, when finch trapping started in the Kimberley, it was the most sought after finch by trappers and the most desired by fanciers. Between the years 1934 and 1939, the Gouldian Finch was the most exported single finch species. The Perth Zoo exported 22,064 finches of which 12,509 were Gouldian. Private dealers exported 35,315 finches, of which 14,504 were Gouldian. In 1958, the most finches taken in any one year were trapped in the Kimberley; of the 38,649 finches taken, 11,286 were Gouldian. In the last year that the Gouldian Finch was legally trapped in Western Australia, of the 23,450 finches taken 1,054 were Gouldian. The Gouldian Finch was fully protected in 1982.[17]